A common mistake when creating overflowing containers with CSS is to use overflow: scroll or it's x/y variants. This will result in scrollbars always showing, even if the content doesn't overflow. This results in "phantom scrollbars" that are useless and only take up space and distract your users.
Keeping your Git branches clean in your local repo is very helpful to make it easy to switch between branches you are currently working on. The last thing you want is a bunch of old branches that have already been merged showing in your list of branches when running git checkout.